While the curtain-like aurorae we see at Earth are green at the bottom and red at the top, NASA's Cassini spacecraft has shown us similar curtain-like aurorae at Saturn that are red at the bottom and purple at the top. This is how the aurorae would look to the human eye.

The color difference occurs because Earth's aurorae are dominated by excited nitrogen and oxygen atoms and molecules, and Saturn's aurorae are dominated by excited forms of hydrogen. Within each element, colors can differ because of atmospheric density, the levels of the atomic version of an element versus the molecular version, and the energy of impacting electrons.